Slickwater fracturing has increased over the past decade with the advent of shale gas plays. Horizontal wells are now the standard with up to 1 million gallons of water in as many as 6 to 9 frac stages per well. The objective is to create as much contact with the reservoir. To pump high-rate fracture stimulation with fresh water or brine, a friction reducer is required. Most friction reducers used in slickwater fracturing are high-molecular-weight polyacrylamide emulsions. These emulsions are easy to disperse and hydrate into water and also easy to pump and meter.
Because these friction reducers are typically pumped at low concentrations (0.5 to 2 gpt), the industry perception has been that these friction reducers are causing little or no damage to the formation. Since polyacrylamides are synthetic polymers, there is a belief that they are difficult to break.
Slickwater fracturing utilizes very large quantities of water with several stages per well which introduces large volumes of friction reducer into the formation. As such, several operators have recently expressed concerns about the possible fracture and formation damage caused by these friction reducers. To minimize formation damage caused by friction reducers, breakers may be required. Some breakers are delayed to allow the friction to be reduced in the tubing where it is most effective. At even low concentrations of 0.25 gallon/1000 gallons of water, results in 250 gallons of potential polymer damage. Once past the perforations, the breaker will break the polymer to reduce the damage. A number of oxidative breakers such as persulfates, organic peroxide and inorganic peroxides have been used. However, there is still a need for an environmentally friendly viscosity breaker for a well treatment fluid that contains a polyacrylamide friction reducer.